Bash Executable Types

Suggestion

🔍 Search Terms

List of keywords you searched for before creating this issue. Write them down here so that others can find this suggestion more easily and help provide feedback.

• Bash
• Shellscript

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn’t be a breaking change in existing TypeScript/JavaScript code
• This wouldn’t change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn’t a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript’s Design Goals.

⭐ Suggestion

A hot new way of constructing types at build time using the worlds most universally beloved language: bash.

Using the bash`…` type you can now run entire bash programs inside of TypeScript.

type FileName = bash`
  find "$PWD"
`

The bash template type constructor would create a union of every stdout line of the embedded bash program.

📃 Motivating Example

Before: Allows all sorts of strings, who knows if this will work at runtime.

async function readFile(fileName: string) {
  // ...
}

After: Only real files can be read from the file system, now you can sleep at night

type FileName = bash`
  find "$PWD"
`

async function readFile(fileName: FileName) {
  // ...
}

💻 Use Cases

• Type-safe file operations
• Keeping your database in sync with your types
• Running Docker inside TS so your types are reproducible
• Fork bombing VSCode

[DanielRosenwasser]

*checks date* I think you have confused 1/4/2021 and 4/1/2021 😅

[jamiebuilds]

There’s another use case! A whole bunch of people need to be reminded to update their copyright year strings, now they can automate that reminder with $ date

type Year = bash`
  date +"%Y"
`

type Copyright = `Copyright © ${Year} Company, Inc.`


function Footer() {
  let copyright: Copyright = "Copyright © 2020 Company, Inc." // ERROR!!!! Happy 2021!!!
  return <p>{copyright}</p>
}